Studies are being carried out on the amino acid sequence of the heavy chain of myosin from rabbit skeletal muscle. The current year's efforts will be focused upon the central part of the molecule including a 37,000 dalton fragment which comprises most of the "neck" of the molecule, and a 21,000 dalton tryptic fragment that contains probable active site residues. The segment of sequence between these fragments represents the "hinge" between the head and neck of myosin. Model building studies of these peptides will be carried out using an Evans-Sutherland computer controlled display system, and attempts will be made to describe the structural basis for some of the functional properties of myosin.